| The electrochemical detection of neurotransmitters and metabolites in vivo has centered on fast-scan cyclic voltammetry (FSCV) due to its subsecond temporal resolution, sensitivity and chemical selectivity. FSCV at carbon fiber microelectrodes (CFMs) is a differential technique that can record phasic (second-to-second) changes in the concentration of electroactive analytes in a microenvironment, such as dopamine neurotransmission in the brain. However, in order to isolate current due to fluctuations in analyte concentration, i.e. to make phasic measurements, the subtraction of a large background current is required. This background current is generated by faradaic and non- Faradaic processes. Its volatility renders FSCV unable to determine absolute or slowly varying concentrations. However, there is still a need to readily determine the absolute or slowly changing concentrations of electroactive analytes in tissue. For example, basal concentrations of dopamine vary throughout the brain and can affect the dynamics of dopaminergic systems.;This research presents a microfabricated electrochemical sensor designed to improve on traditional FSCV at CFMs by adding the capability for absolute concentration measurements. The sensor design is small enough to integrate into an existing in vivo platform. The sensor is a collector-generator assembly comprised of carbon band electrodes spaced several microns apart. Absolute concentration sensing works by varying the potential of the generator electrode to manipulate local concentrations of electroactive species in the solution. These changes are measured at the adjacent collector electrode with FSCV and used to determine the absolute concentration in the solution. As a proof of concept, the sensor was used to determine absolute concentrations of ascorbic acid, an important reducing agent and metabolite. (Abstract shortened by ProQuest.). |
